Chatway Live Chat

Update Custom Data

update-custom-data

Destructive

Replace the value of an existing custom field on a Chatway visitor/contact. Use add-custom-data when the field does not exist. Use view-custom-fields to check the exact field name first.

Input Schema

TableJSON Schema

Name	Required	Description
`name`	Yes	Name of the existing custom field to update, up to 100 characters.
`value`	Yes	New value that replaces the current one, up to 1,000 characters.
`visitor_id`	Yes	UUID of the visitor/contact, for example `contact.id` from `get-conversation` or `id` from `search-contacts`.

Output Schema

TableJSON Schema

Name	Required	Description
`name`	No	Custom field name.
`value`	No	New stored value.
`visitor_id`	No	Visitor/contact UUID.

Schema Changelog

Changes observed during successful MCP inspections.

Changed4 schema fields changedOct 15, 2026

addedInput schema / properties / name / description

Added value: +"Name of the existing custom field to update, up to 100 characters."

addedInput schema / properties / value / description

Added value: +"New value that replaces the current one, up to 1,000 characters."

addedInput schema / properties / visitor_id / description

Added value: +"UUID of the visitor/contact, for example `contact.id` from `get-conversation` or `id` from `search-contacts`."

changedOutput schema / (root)

Previous value: -nullNew value: +{
+  "properties": {
+    "name": {
+      "description": "Custom field name.",
+      "type": "string"
+    },
+    "value": {
+      "description": "New stored value.",
+      "type": "string"
+    },
+    "visitor_id": {
+      "description": "Visitor/contact UUID.",
+      "type": "string"
+    }
+  },
+  "type": "object"
+}

First observedOct 15, 2026

TDQS

A4.3/5.0

Behavior3/5

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Annotations already declare destructiveHint=true and readOnlyHint=false, so the overwrite semantics are covered. The description reinforces replacement ('replaces the current one' in the schema) and adds the precondition that the field must already exist, but says nothing about irreversibility, permission requirements, or failure modes when the field name is wrong.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness5/5

Is the description appropriately sized, front-loaded, and free of redundancy?

Three short sentences, zero waste, with the core action front-loaded and the disambiguation guidance following immediately.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness5/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

An output schema exists, so return values need not be explained. Purpose, sibling routing, and the field-must-exist precondition are all present, leaving nothing an agent needs in order to invoke it correctly.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters3/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema description coverage is 100%, so all three parameters (name, value, visitor_id) are already documented with length limits and UUID sourcing. The description adds only a cross-reference to view-custom-fields for the name parameter, which is modest value over the schema baseline.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose5/5

Does the description clearly state what the tool does and how it differs from similar tools?

States a specific verb and resource: 'Replace the value of an existing custom field on a Chatway visitor/contact.' It explicitly scopes to replacing an EXISTING field, which cleanly separates it from the sibling add-custom-data that creates new fields.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines5/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

Gives both alternatives and the conditions that select them: use add-custom-data when the field does not exist, and view-custom-fields to verify the exact field name first. An agent can route correctly without inspecting other schemas.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.

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